Ricardo Rojas

EDTA modified LDHs as Cu2+ scavengers: removal kinetics and sorbent stability.

EDTA modified layered double hydroxides (LDHs) were investigated as potential sorbents to remediate heavy metals pollution. The polidentate ligand was introduced by an exchange method in a Zn-Al-LDH, which takes place with partial erosion of the layers, causing the intercalation of [Zn(EDTA)](2-) complex instead of the ligand. [Cu(H(2)O)(6)](2+) cation was selected as a model cation to study the uptake mechanism, exploring the elimination kinetics from the first minutes up to the steady state. A flow injection analysis system coupled to an amperometric detector (FIA-AM) was applied to perform fast and reliable [Cu(H(2)O)(6)](2+) determinations in monodisperse solid-aqueous solution systems. Furthermore, the sorbent stability was determined as a function of the pH and the nitrate concentration. The [Cu(H(2)O)(6)](2+) elimination is produced by an exchange reaction with [Zn(EDTA)](2-) anions placed either in the solid interlayer or in the aqueous solution, this last being released from the sorbent. Additional [Cu(H(2)O)(6)](2+) removal is produced by Cu(OH)(2) precipitation at high copper concentrations due to the LDHs high pH buffering capacity. The sorbent removes [Cu(H(2)O)(6)](2+) with high affinity in a wide concentration range. The elimination process reaches equilibrium in less than 30 min and leaves metal cation concentrations lower than 0.05 ppm in the supernatants.

Dissolution kinetics and mechanism of Mg–Al layered double hydroxides: A simple approach to describe drug release in acid media

Layered double hydroxides (LDHs) weathering in acidic media is one of the main features that affects their applications in drug delivery systems. In this work, the dissolution kinetics of biocompatible Mg-Al LDHs was studied at different initial pH values and solid concentrations using a simple and fast experimental method that coupled flow injection analysis and amperometric detection. A carbonate intercalated sample was used to determine the controlling step of the process and the dissolution mechanism. Finally, the study was extended to an ibuprofen intercalated LDH. The obtained results showed that the weathering process was mainly controlled by the exposed area and surface reactivity of LDHs particles. The dissolution mechanism at the particle surface was described in two steps: fast formation of surface reactive sites by hydroxyl group protonation and slow detachment of metal ions from surface. At strongly acidic conditions, the reaction rate was pH dependent due to the equilibrium between protonated (active) and deprotonated (inactive) hydroxyl groups. On the other hand, at mildly acidic conditions, the dissolution behavior was also ruled by the equilibrium attained between the particle surface reactive sites and the dissolved species. LDHs solubility and dissolution rate presented strong dependence with the interlayer anion. The ibuprofen intercalated sample was more soluble and more rapidly dissolved than the carbonate intercalated one in acetic/acetate buffer. On the other hand, the dissolution mechanism was invariant with the interlayer anion.

Size-tunable LDH–protein hybrids toward the optimization of drug nanocarriers

Layered double hydroxides (LDHs) are extensively investigated as drug nanocarriers due to their anion exchange properties and potential capacity to achieve enhanced cellular trafficking and targeted delivery. In this work, LDH-protein hybrids with controlled particle size were obtained by modulation of the charge and hydrophobicity of LDH matrixes. In order to do that, bovine serum albumin (BSA) adsorption was studied in LDH matrixes intercalated with chloride and dodecylsulfate (DS-) in different ratios and its dependence on pH and ionic strength was determined. Positively charged LDH-Cl matrixes in aqueous solution changed from micro- to nano-size when adsorbing BSA molecules at pH values higher than the isoelectric point of the protein. On the other hand, the low BSA hybridization with a negatively charged LDH-DS matrix was not enough to reduce its particle size. However, a fine tuning of the physicochemical properties of the LDH-Cl matrix by controlled DS- incorporation and pH and ionic strength conditions allowed LDH-BSA nanohybrids to be partially intercalated with the surfactant that exhibited colloidal stability at high ionic strength (similar to that of biological fluids).

Relevance of protein–protein interactions on the biological identity of nanoparticles

Considering that the use of nanoparticles (NPs) as carriers of therapeutic or theranostic agents has increased in the last years, it is mandatory to understand the interaction between NPs and living systems. In contact with biological fluids, the NPs (synthetic identity) are covered with biomolecules that form a protein corona, which defines the biological identity. It is well known that the protein corona formation is mediated by non-specific physical interactions, but protein-protein interactions (PPI), involving specific recognition sites of the polypeptides, are also involved. This work explores the relationship between the synthetic and biological identities of layered double hydroxides nanoparticles (LDH-NPs) and the effect of the protein corona on the cellular response. With such a purpose, the synthetic identity was modified by coating LDH-NPs with either a single protein or a complex mixture of them, followed by the characterization of the protein corona formed in a commonly used cell culture medium. A proteomic approach was used to identify the protein corona molecules and the PPI network was constructed with a novel bioinformatic tool. The coating on LDH-NPs defines the biological identity in such a way that the composition of the protein corona as well as PPI are changed. Electrostatic interactions appear not to be the only driving force regulating the interactions between NPs, proteins and cells since the specific recognition also play a fundamental role. However, the biological identity of LDH-NPs does not affect the interactions with cells that shows negligible cytotoxicity and high internalization levels.